Photographic emulsion



s dissolving a color former fast to diffusion, 12. The process as defined in claim 9, wherein water containing a water-soluble alkali, in the the color former is fast-to diffusion by virtue of ce of a compound-selected from the class the presence therein of an aliphatic chain of ting of bile acids and salts thereof, mixing more than 5 carbon atoms. solution with a silver halide emulsion and 5 The comppsition as d ne n l i 4, mg the resulting i tu wherein said compound is a salt of cholic acid. 11; The process as defined in claim 10, wherein ALFRED mbmacns ewater-soluble alkali is caustic soda. WILI-IELM SCHNEIDER.

. ted July 20, 1943 Delaware on for color photography. the production of color photographic images image dyestuif is often directly or'indirectly W by means of a silver image from dyestuif w ponents one or several of which'have already incorporated into the silver halide emulsion exposure. In multi-layer materials it is ry in order to obtain an unobjectionable eparation that the dyestuflf components ast to difiusion 'with respect to the layercolloid, for instance, gelatin, i. e. that do not diffuse from layer to layer or from layers into the photographic baths during reduction of the layers and the treatment "1' in the baths even if they are added to emulsion in a soluble form. This fastness usion of the dyestuff formers may, for ine, be effected by their special chemical conon or by the introduction into the molecule in radicles. Dyestufi formers made fast pswhich essentially increase the molecular ht thereof often are sparingly water-soluble.

sparingly soluble dyestuff formers have the vantage that it is diflicult to keep them in dissolved condition when added to the phophic emulsion and when drying them to-.- e with the gelatin'to give a clear translayer. It has, therefore, already been (1 to disperse these water-insoluble or ly water-soluble dyestuff formers with wetting or dispersing agents such as sulhigh molecular weight hydroxy fatty acids lcohols, high molecular weight aliphatic es or resin soaps. The effect of these addiuce a strong decrease of the surface tension n the substance to be dispersed and the rflas the solvent so that the substance is intensely wetted whereby its emulsiflcation ned and its recrystallization or resepararom the emulsion is prevented or at least ,diificuit. It is evident that the difilcultly l dyestufl formers which are to be emulsithis manner have a great tendency to te from the solution so that it is necessary considerable amount of dispersing agents photographic emulsion in order to render ble a separation and agglomeration of dyestufl components. The photographic owever; is very sensitive to foreign sub- Moreover traces of crystals and flakes e gelatin layer even if so small that they ltllflusion by substituting the same with 'such' UNITED STATES PATENT oFncE PHOTOGRAPHIC EMULSION Alfred Friihlich and Wilhelm Schneider, Germany, assignore to General Aniline Corporation, New York, N.v Y., a corporation of Dessan, aFilm 13 Claims. (01. 95-6) present invention relates to a photographicv on and more particularly to a silver halide can be scarcely distinguished with the naked eye cause much trouble in projection. It is, therefore, desirable to dissolve the water-insoluble dyestuil formers directly in the photographic emulsion.

' Our present invention is based on the observation that water-insoluble or sparingly water-soluble dyestuif components can be dissolved in agents preferably is a physical one for they to diffusion with respect to the binding agent (gelatin) of the emulsion by dissolving the components in water inthe presence of bile acids or salts thereof, if necessary with an addition of organic solvents. It is sometimes helpful to warm the substances while dissolving them. The solution obtained can be added to a photographic emulsion or a gelatin solution without effecting a precipitation or aturbidity of these aqueous liquids. On drying the gelatin solution a layer clear as glass is obtained. By this invention it is accordingly possible to keep in solution dyestuff formers which have heretofore been thought -useless since they could not be added in a dissolved condition to an emulsion due to their low solubility or their tendency to crystallize ondrying the emulsion to give a layer. It is furthermore possible to form layers clear as glass with such dyestufl formers.

'Ilhe dyestui! formers are conveniently dissolved together with the bile acid or a'watersoluble salt thereof, if desired, with an addition 1 of the dyestufi former is added. The solution of the dyestuil' former may also be mixed with a gelatin solution whereupon, if necessary, after washing with water, the resulting solution is worked up into a silver halide emulsion.

The dyestufl formers used in the practice of this invention are, for instance, of the general types described. in the following patents and applications:

U. S. Patents 2,186,852, 2,186,719, 2,186,734, 2,186,851, 2,186,733, 2,186,732, 2,186,847 dated January 9, 1940, U. S. Patents 2,179,238, 2,179,244, 2,178,612 dated November 7, 1939, French Patents 344,648, 344,649, 844,637, U. S. Patents 2,280,722, 2,292,575, 2,303,928 and 2,307,399 and U. S. Patent applications Ser. No. 284,258 filed July 13, 1939, Ser. No. 333,814 filed May '7, 1940, Ser. No. 335,144 filed May 14, 1940, Ser. No. 341,180 filed 

